Open access books show more overall usage

In the first instance, we compare the average number of downloads, citations and unique domains (referencing the books) across OA and non-OA books as two groups. We also draw parallel comparisons of the two groups across book types and discipline clusters. These are summarized in Figure 1.

OA books as a group have on average ten times more downloads than non-OA books (first pair of bars in the top panel). There are more than double the number of citations for OA books. To a lesser extent (proportionally), there is also on average a higher number of unique web domains referencing OA titles. Higher levels of usage (via all three proxies) for OA books are also observed across each of the groups by book type and discipline cluster. It can be seen that the magnitudes of difference for each metric across OA and non-OA books vary across the different groups. For example, the difference between downloads of OA books and non-OA books seems to be amplified for the biomedical sciences. Given our sample these differences could be specific to Springer Nature or may reflect differences in disciplinary usage. Further work will be required to identify the driving factors. However, there is a consistent pattern across the different groups that OA books are seeing more usage.

The number of citations is a useful proxy of academic usage, while web visibility provides insight into how the books are being used on the web: either as linked text or references. These are additional proxies of usage to the number of downloads for books. The presence of higher levels of usage signalled by all three proxies suggest that OA books are not only being downloaded more often than their non-OA counterparts, but are also being read, used, referenced and attracting attention in different ways. This strengthens the case for a usage effect that is related to OA specifically.

The top panel compares average numbers of downloads, citations and web visibility across all OA books and all non-OA books in our sample. Download numbers are provided in 1,000s and vertical lines are the 95% confidence interval for each metric. Parallel comparison across book types and discipline clusters are given in the subsequent panels. Each panel includes relevant books published in 2015, 2016 and 2017. There are no OA books in the brief category for biomedical sciences.

Open access books show more usage over time

We are also interested in comparing the download levels over the lifetimes of the books. Using the times recorded for downloads and the publication dates of each book, we are able to provide the time series of downloads per month over 40 months from the date of publication. These are summarized in Figure 2, showing overall trends comparing all OA to all non-OA books in the corpus, and for each variation of book type and discipline cluster.

The number of downloads is displayed in log-scale, meaning the magnitude of differences are even greater then shown. The 95% confidence bands for downloads are shown in the top panel, which compares downloads over time for all books in the sample. Each panel includes relevant books published in 2015, 2016 and 2017. Some books have usage data from prior to the official release date so show usage prior to zero months. We do not have specific explanations for the spikes in usage evident in some panels, although high measured usage in the first month of release is common (see e.g. Business and Economics, and Biomedical Monographs). Spikes in usage later in the life of books could be a result of high usage of a specific book (e.g. as a result of its use as a reading in a massive online open course, or MOOC).

The top panel shows clear evidence of OA books having an advantage in the number of downloads over time. For all 40 months in the analysis, OA books have recorded significantly more downloads than their non-OA counterparts. That is, not only do OA books have a higher number of downloads to begin with, but this effect is also persistent over time.

This general pattern carries over to subsets of books by book type and discipline clusters. Again, there are variations across groups but persistently higher downloads for OA books. It is also interesting to note that many groups of OA books seem to enjoy a more impactful starting point (noting the sudden shock of downloads at time zero with log-scale number of downloads displayed in many of the panels in Figure 2).

Open access books show usage in a wider range of countries

By analysing the geolocation of downloads, we are able to provide comparisons of book usage across countries. For each book, we record the number of downloads from each country. Subsequently, we can calculate the number of downloads per book for any specific country. We do this for the set of all OA books included in our study and for the non-OA books. The results are visualized in Figure 3.

Evidently the usage (via downloads) of both non-OA and OA books is international and spans the globe. Usage of non-OA books is identified in 118 countries (by definition these are all countries with licensed access to Springer Nature content). In contrast, usage of OA books is identified in 201 countries. For both OA and non-OA books the highest levels of usage are seen in the USA, UK, Germany and mainland China. With only a few exceptions, OA books see higher levels of usage across the globe. There is also evidence that OA books see more average downloads from some African and Latin American countries that otherwise had very little access to non-OA titles.

An important aspect to consider is the role of population size in the geographical patterns of usage. One challenge with the analysis of academic usage is to identify a good proxy of ‘academic population size’. Examples of this include normalization by the country’s number of people in tertiary education, overall academic output size and total number of citations. We provide one such example through normalizing the downloads by total number of publications (see Supplementary Materials for details on this data). This is visualized in Figure S1 of the Supplementary Materials.

While total publication size is not a perfect proxy for the number of potential academic readers of the books, this normalization suggests that ‘usage per academic work’ for both OA and non-OA books is fairly consistent across North America and North Western Europe, as well as mainland China, South Africa and Australia. Focusing on other geographical regions, and consistent with the overall download counts (see Figure S1 of the Supplementary Materials), Egypt emerges as a heavy user of non-OA content relative to overall academic outputs, along with Uruguay, Ethiopia and Uzbekistan. Relatively heavy users of OA content relative to academic output size include Somalia, Afghanistan, Bhutan, Niger and South Sudan.

Average usage by country across the whole corpus for OA (top) and non-OA (bottom) books. Several countries show a greater concentration of usage for OA books and these countries are predominantly in the southern hemisphere. Both maps are on the same colour scale (in log-scale).

Open access books show increased usage for underserved populations and low to middle income countries

Overall, we find OA books having to reach more countries globally than non-OA books. Figure 3 also presented some evidence that OA books see improved usage for traditionally underserved countries and low to middle income countries. To explore this in more detail we focus on the anonymized downloads, which are solely attributed to OA books (as non-OA books can only be accessed if subscribed to, i.e. logged access). In particular, we can examine usage in countries that do not otherwise have access to Springer Nature books in digital formats. Usage of OA books was identified in a wide range of countries that recorded zero usage of the non-OA books in the dataset. Of these countries where only OA books recorded usage, over 20 were from Africa. Usage of OA books from countries that do not otherwise purchase Springer Nature e-book titles totalled 118,247 downloads, representing 1% of the total anonymous usage of OA titles.

A wide range of countries with zero logged usage show anonymous usage (see Figure 4) with a total of 118,247 downloads representing 1% of the total anonymous usage. Of those countries, more than 20 were from Africa, with others mostly in the Middle East and South East Asia. Countries with low GDP and development are significantly represented in this group.

Open access books show higher diversity of usage

While we have provided evidence for wider usage of OA books (i.e. more countries download OA books), it is also important to understand the level of disparity amongst country usage. We can provide a more quantitative measure of this effect by examining a disparity index. That is, how much usage deviates from the situation where all countries show even usage. The Gini coefficient is a disparity index that is often used to define levels of income inequality. We can use the same calculation to measure inequalities in geographical usage and use this to compare OA and non-OA books. A lower Gini coefficient indicates more diverse usage. That is, a lower number means lower inequality, or if preferred, greater equality. The Gini coefficient is calculated for every book in our sample. Figure 5 shows a summary of these results for OA and non-OA books overall, and for different combinations of book type and discipline cluster.

For the overall corpus, and for every individual category, the usage by country is substantially more diverse for OA books. This form of analysis may be useful in identifying books that have significant potential to reach diverse geographic audiences. It might also be interesting to examine whether a low Gini coefficient for a non-OA book suggests potential for substantially enhanced usage if the book were converted to OA. It should be noted that there are outliers amongst both OA and non-OA books in terms of their values in the Gini coefficient. In particular, there are exceptional books in both categories that may have broad interest (e.g. A Theory of Philosophical Fallacies) or narrow geographical focus (e.g. A History of Male Psychological Disorders In Britain, 1945–1980).

The Gini coefficient is a statistical measure of inequality. Here the coefficient is calculated for the contribution of each country to the overall usage of each book. A lower Gini coefficient means more diverse usage. The median Gini coefficient and the 95% confidence interval are shown. For the corpus as a whole and for every category, the median Gini coefficient of OA books is lower, meaning that the geographical usage of OA books is more diverse (i.e. less unequal).

Open access books associated with a larger title effect on geographic usage

Approximately 16% of the whole corpus of books in this study had a region or country name in their title or subtitle. The proportion of OA versus non-OA books with a geographic reference in the title is approximately the same. We hand coded title-references to countries or regions, including variations referring to language (e.g. ‘Chinese’) and regions (‘Africa’, ‘Latin America’ as well as possessives such as ‘sub-Saharan’ and ‘Latin American’) and examined the usage from those regions, focusing on Africa and Latin America as examples. We are interested in discovering whether there is a ‘title’ effect, i.e. a book with a title referencing a region shows greater usage in that region, and if this effect differs across OA and non-OA books.

In Figure 6 we show the relative increase in downloads for books referencing Africa in their titles. We calculate the expected downloads per book for each country from the whole dataset and divide the actual usage for those with ‘Africa’ in the title by the expected downloads. A value of five indicates that there are five times more downloads for books referencing Africa in the title in a given country than is expected based on the whole dataset (or the set of non-OA or OA books respectively). The three panels show download patterns for all books, OA books and non-OA books, respectively. Parallel visualizations for books referencing ‘Latin America’ are provided in Figure S2 of the Supplementary Materials.

For Africa and Latin America, we see a substantial increase in usage overall from those regions featuring in the title. In both cases there is also some evidence of increased usage in some parts of the other region (e.g. increased usage in a small number of African countries for titles that have Latin America in the title). In the case of books with ‘Africa’ in the title there is increased Latin American usage in Guyana, Suriname, Venezuela and Panama. Other countries with increased usage are Laos, the Solomon Islands and Timor-Leste. It should be noted that many of these countries have relatively low usage so the changes may not be significant in statistical terms.

The size of this geographic title effect is substantially larger for books that are OA. OA books about Africa are widely read beyond Africa as well as in Africa. There is a very large increase in usage compared to the whole sample across the African continent. By contrast, non-OA books with ‘Africa’ in the title show a usage increase only in South Africa, Uganda, Ethiopia and Sudan. Not only is OA associated with increased usage in countries under-represented in global scholarship, but it is also associated with increased global usage of scholarship about under-represented countries. See the case study in the Supplementary Materials for an example of the enhancement of usage for a book with a specific country in the title.

Similar effects are seen for Latin America, although the enhancement is not quite as localized as in the case of Africa. Usage in Latin America is substantially greater for all books with ‘Latin America’ (including variations and possessives such as ‘Latin American’) in the title. The size of this increase is substantially larger for OA books. In addition, there is broader usage internationally for the OA books. The overall effect is larger for books with ‘Latin America’ (maximum of 100 times more usage) than it is for ‘Africa’ (maximum increase of fivefold).

Overall usage for each country of books referencing ‘Africa’ in the title was divided by usage for that country for the full corpus (or for the set of OA or non-OA books respectively). Increases in usage are shown, with a value of five meaning there are five times the number of downloads for books referencing Africa in the title. Countries showing unchanged or decreased usage are displayed in the lightest shades. OA books show a greater increase across a range of countries, with the increase concentrated in Africa.

Anonymous usage versus logged usage

Recall that usage (via downloads) for OA books can be categorized as logged access or anonymous access. In fact, we see significant differences in usage numbers across these two types of access. The overall amount of anonymous usage is always greater than logged usage for each book: generally, twice as much (with exceptions for only a small number of books in our study).

We cannot directly ascribe anonymous usage to ‘general public’ or ‘non-academic’ usage because a proportion of this will be off-campus or personal device usage by scholars. However, there are differences in the patterns of usage at the country-level. Anonymous usage is higher in Kenya, Brazil, India and Iran. Logged usage is comparatively higher in Egypt. We have already noted that there is substantial anonymous usage in countries for which there is no logged usage (see Figure 4). There is also a wide range of countries with a very high proportion of anonymous usage, despite these countries including institutions that have access to non-OA content. This list includes Syria, Ukraine, Georgia, Guatemala and Sri Lanka. The distribution of downloads across countries for each type of access is displayed in Figure S3 of the Supplementary Materials.

Web visibility across top level domains (TLDs)

In this study we use the number of unique domains determined by webometrics analysis as a proxy for web visibility. While OA books display higher levels of web visibility overall and for various categories of books (see Figure 1), these differences are proportionally much less than those seen for downloads and citations.

We can examine geographical aspects of this web visibility by looking at the top level domains (TLDs), the part of a URL after the last ‘dot’ in the domain name. While we cannot ascribe a geographical location to common TLDs such as .com and .org, many domain names can be associated with countries. Broadly speaking the geographical representation of pages that refer to books in the corpus is consistent with the usage via downloads and citations, with European (.uk, .de, .it), North American (.edu, .ca) and Australian (.au) TLDs (^{Note 6}) dominating (see Table S1 of the Supplementary Materials). The top ten TLDs constitute 80% of all web pages identified for the whole corpus of books. Overall, the difference between the number of websites and the range of TLDs between the OA and non-OA books shows a 39% increase in unique domains referencing the OA books versus non-OA titles (with the increases for each of the top ten TLDs displayed in Figure S4 of the Supplementary Materials). This is a relatively small increase compared to the tenfold effect on downloads and more than doubling of the number of citations.

Springer Nature has well-established and effective pathways for marketing and digital dissemination which are applied to both OA and non-OA titles. The small effect of OA on the number of websites referring to these titles is most likely to be a result of the fact that both OA and non-OA titles benefit from these processes.